AP BIOLOGY ANIMAL NEWS
MAY 8, 2014
The Polar Bear The predator of the Arctic Circle. This animal is at the top of its food chain, but there is more to the polar bear than meets the eye. Project by: Alejandro Anderson and Patrick Huggins
The image to the right is of a polar bear in its natural habitat. Polar bears are known for resting on chunks of ice while swimming in the Arctic Ocean. May 8, 2014 – The scientific name of the polar bear, Ursus maritimus, translates from Latin to “sea bear”. As this name would suggest, the polar bear is linked to the Arctic Ocean environment, and is dependent on the seal it hunts oﬀshore. Balancing on sheets of ice between dives, polar bears are actually quite bulky, using their fat stores as insulation and a source of energy. Males can weigh in anywhere from 500 to 1,750 pounds, while the smaller females weigh about 330 to 550 pounds. ! The polar bear species originated in the Arctic Circle. Polar bears are thought to have evolved from an isolated population of brown bears at some point in the ice age between 100,000 to 250,000 years ago, during the mid-Pleistocene period. During this time period, glaciers covered almost all of Europe, Asia, and North America. In fact, the Arctic Ocean was completely frozen. It is
believed that the brown bears were in search of food and wandered across these glaciers. About 125,000 years ago, the brown bears that were located in the Arctic Circle found themselves isolated due to the shifting glaciers. Polar bears currently live in the arctic tundra, specifically in northern North America, and Northern Asia. These are Arctic areas located just south of the northern polar ice cap. ! Polar bears are NOT found in Antarctica. However, the environment they live in is similar to that of Antarctica's: extremely cold, and only welladapted organisms can survive because of the harsh conditions. The arctic tundra got its name from the Finnish word “tunturia” which refers to a treeless plain. That is what the arctic tundra is, cold, icy, windy, extremely sunny in the summer, extremely dark during the winter, treeless, and founded on permafrost. The permafrost is a thick subsurface of soil that remains frozen year round. During the winter, the temperature is around -29 F (34 C). During the summer, the temperature is around 29 F (-1.7 C).
AP BIOLOGY ANIMAL NEWS It isn’t uncommon for the temperature to plunge down to -58 F (-50 C) during the winter. Most of the area averages around 20 inches of precipitation (mostly in the form of snow/ice), while parts of Greenland see around 47 inches of precipitation every year. There are about 1,700 diﬀerent species of plants that live in the arctic tundra. These includes, flowering plants, herbs, mosses, grasses, small shrubs, and lichens (similar to fungi and algae). Other animals that live in the arctic tundra include the snowy owl, Canada lynx, tundra swan, arctic hare, arctic fox, beluga whale, caribou, narwhal, and seal. The biome does not experience many natural disasters. Blizzards are the most common natural disasters that occur. However, the arctic tundra has been facing problems and drastic weather changes as a result of global warming. The temperature has increased, the ice has been melting, and the plants and animals are seriously aﬀected. The permafrost has continued to melt and thaw out. The melting of the permafrost releases more greenhouse gases, and many of the plants and animals are struggling to adapt to the drastic changes.
MAY 8, 2014 ! The polar bear resides along the coastal areas of northern North America, Greenland, and northeast Asia. Polar bears even live on moving masses of ice. The only density-dependent regulators that aﬀect polar bears are global warming and competition for resources. Global warming has aﬀected the number of living polar bears in the Arctic. It has melted many of the ice masses that were once homes to the polar bears, which has led to a decrease in polar bear population. This problem has grown significantly and has caught the attention of many nations and their citizens. Even though the polar bear is not at the top of the endangered species list, if the temperatures of the planet continue to go up, the polar bear population will drop even further. Additionally, competition for resources has increased amongst the polar bear population. Food can be scarce, from a lack of seals, to a lack of edible vegetation. There is a limited amount of food sources for polar bears in the Arctic Circle.
Polar Bears: Top of the Food Chain ! Male polar bears dominate a territory that includes the territories of multiple female polar bears. As an apex predator, the polar bear does not have any adaptations to defend itself from any natural predators. However, when males come in contact with one another, they often compete over mates with violent fighting. These fights can drag on for several weeks, and result in death or severe, long-lasting wounds for both bears. Females that refuse to mate with males may be attacked or abused. These female polar bears receive scratches and bite marks from mating refusals and from defending their cubs from violent males. Less often, orca whales have been known to kill and eat polar bears that are caught while swimming. Humans, while not a natural predator of polar bears, will occasionally hunt them as trophies. Despite a lack of natural predators on a higher trophic level, the polar bear population is shrinking. Even more threatening is the fact that genetic diversity amongst the diminishing polar bear population is dangerously low.
AP BIOLOGY ANIMAL NEWS
MAY 8, 2014
! The polar bear treats all other species it encounters as its prey. However, when there is an abundance of seal, the polar bears will only eat their prey’s fat, leaving the flesh for arctic scavengers. The polar bear’s diet mainly consists of seal and the carcasses of beluga whales, walruses, and grey and bowhead whales. On land, polar bears will hunt muskox and reindeer as well as waterfowl and rodents. They will also scavenge for kelp, shellfish, eggs, berries, and human garbage.
indirect impacts on the species. In addition to constantly monitoring the populations of polar bears, humans are working towards living more sustainable lifestyles. By consuming less energy, people can reduce their carbon output, dangerous to apex predators, thereby lessening their because the concentration of toxic contribution to the melting of substances increases as energy polar ice. passes up each trophic level. ! As the top predator of the Pesticides and other industrial arctic tundra, polar bears serve as toxins filter up the food chain and an ambassador to a region of our are found in high concentrations planet responsible for global in polar bears’ bodies and milk. climate and sea levels. Any slight This toxic milk may directly changes to the bottom of their poison and kill young cubs. The food chains become noticeable pollutants’ eﬀects on the polar THE HUMAN IMPACT eﬀects among the polar bear bears’ bodies range from low ! Humans have had a direct population. In this respect, they immune systems to and multi-faceted impact on the act as a measuring stick of human pseudohermaphroditism in decline of polar bears. Human impact, giving us a biological females. From human presence contribution to the climate change perspective on our impact on the alone, oil exploration in the arctic known as “global warming” is the polar ice caps. By closely disturbs the polar bear most noticeable of these. In the observing these creatures in populations. Any oil spills are southernmost polar bear collaboration with climate extremely diﬃcult to contain in territories, warmer temperatures observation and measuring the the harsh environment. Oil are leading to fewer weeks of the recession of the polar ice caps, contamination of polar bear year in which ice conditions are humans will be able to more territory can poison the bears or suitable for hunting. Without the accurately understand the changes soak the fur coats of the animals. ice as a hunting platform, polar occurring on the planet. Polar bears with oily coats cannot bears must wait longer to begin conserve heat as eﬀectively, and their hunting season and return to they burn more calories each shore earlier. For every week of hour to stay warm. On top of hunting they miss, they will have these indirect detriments to the 22 fewer pounds of body fat than species, humans will they naturally would. This has led occasionally hunt polar bears to local extinctions in southern for their fur and meat. Humans polar bear territory, caused almost are intervening in the stability entirely by starvation and low milk of the polar bear population by production for cubs. Human working to reverse their negative pollutants are often most